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motor mount: plug on both or just one?

I searched a bit and didn't find anything definitive and the car is at a friends house so I can't just run out and check. help please?

I have the car in service position (see the low oil pressure thread). My driver side motor mount is leaking so I ordered new ones to do before I put it all back together. Only one of the new mounts has the plug, I was under the assumption from the pics on the website that they both have the plug. so did I get a bad mount or does only one side have the plug?

But in my car neither did ( 2014 ) but I bought the one with the plug anyway and just threw it in. Neither were leaking ( maybe they got rid of those and its solid ) . but I replaced because the aluminum housing just rotted off.

What's curious is the diagram for the 2.0T from May 2008 references only a N144, left engine mount valve.
For the 3.0T from Nov 2008, 2.0T from Nov 2011, and 3.0T from Nov 2011, both the N144 (left) and N145 (right) are referenced.
But my 2009 does have plugs on the left and right side. Wonder if the right side wiring is there but not actually implemented.

has magnetic fluid in it, an electrical current polarizes the fluid and it stiffens the mount.

This is an explanation I found about how they work when I did mine some time ago.

"the way the mounts work is that there is a fluid chamber with a plastic body in the middle of it, with small channel cut through it. this allows fluid from the top chamber, through the plastic body, to the bottom chamber. the bottom chamber is rubber lined and can deform under pressure. there is also an airway vented to atmosphere, with a rubber membrane separating the fluid from the atmosphere. a solenoid valve, controlled by the motronic, can open or close the airway.

below 1100 rpm (i.e idle), the engine vibrations are not enough to force fluid from the top chamber, through the passageway to the bottom chamber. the airway is open (solenoid valve open). the rubber membrane creates a soft cushion which absorbs the high frequency vibrations.

above 1100 rpm the soleniod valve is closed which blocks the airway and so "hardens" the mount (the fluid has nowhere to go). thus the mount is effectively solid.

the high frequency vibrations at speed are absorbed by the membrane (as in the idle case), while the more damaging low frequency vibrations cause the fluid to force itself through the chamber in the plastic body to the lower chamber, forcing the (lower) rubber chamber to distort - effectively absorbing the vibrations."

This is an explanation I found about how they work when I did mine some time ago.

"the way the mounts work is that there is a fluid chamber with a plastic body in the middle of it, with small channel cut through it. this allows fluid from the top chamber, through the plastic body, to the bottom chamber. the bottom chamber is rubber lined and can deform under pressure. there is also an airway vented to atmosphere, with a rubber membrane separating the fluid from the atmosphere. a solenoid valve, controlled by the motronic, can open or close the airway.

below 1100 rpm (i.e idle), the engine vibrations are not enough to force fluid from the top chamber, through the passageway to the bottom chamber. the airway is open (solenoid valve open). the rubber membrane creates a soft cushion which absorbs the high frequency vibrations.

above 1100 rpm the soleniod valve is closed which blocks the airway and so "hardens" the mount (the fluid has nowhere to go). thus the mount is effectively solid.

the high frequency vibrations at speed are absorbed by the membrane (as in the idle case), while the more damaging low frequency vibrations cause the fluid to force itself through the chamber in the plastic body to the lower chamber, forcing the (lower) rubber chamber to distort - effectively absorbing the vibrations."

oh wow then I guess not all VAG cars do it the same way.. that is interesting stuff, im cutting open my old mounts then for a look see..

I've not seen this code, but have read that others with B8's have encountered an N144 fault code....Engine Mount Solenoid Valve Open Circuit. I replaced mine about 2 years ago and based on the info I found assumed that there is a solenoid inside the casting. I did open the rubber bellows to check out the diaphragm but never opened the casting, so can't confirm the existence of a solenoid. I've seen pics of other mounts that have a solenoid mounted on the outside.